Lung injury after hepatoenteric ischemia-reperfusion: role of xanthine oxidase

Effect of silibinin on the expression of MMP2, MMP3, MMP9 and TIMP2 in kidney and lung after hepatic ischemia/reperfusion injury in an experimental rat model

PURPOSE

The protective effect of silibinin on kidney and lung parenchyma during hepatic ischemia/reperfusion injury (IRI) is explored.

METHODS

Sixty-three Wistar rats were separated into three groups: sham; control (45 min IRI); and silibinin (200 μL silibinin administration after 45 min of ischemia and before reperfusion). Immunohistochemistry and real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) were used to evaluate the expression levels of MMP2, MMP3, MMP9, and TIMP2 on kidney and lung.

RESULTS

Comparing sham vs. control groups, confirmed that hepatic IRI increased both renal and lung MMP2, MMP3, MMP9 and TIMP2 expressions starting at 180 min (p<0.001). Comparison of the control vs. silibinin groups showed a statistically significant decrease in the expression levels of MMP2, MMP3, and MMP9 and increase of TIMP2 in kidney and lung parenchyma. The starting point of this decrease was at 120 min after reperfusion, both for kidney and lung parameters, and it was statistically significant at 240 min (p<0.001) for kidney, while silibinin showed a peak of lung protection at 180 min after hepatic reperfusion (p<0.001).

CONCLUSIONS

Hepatic IRI causes distant kidney and lung damage, while a statistically significant protective action, both on kidney and lung parenchyma, is conveyed by the intravenous administration of silibinin.

Clinical Multi-Omics Study on the Gut Microbiota in Critically Ill Patients After Cardiovascular Surgery Combined With Cardiopulmonary Bypass With or Without Sepsis (MUL-GM-CSCPB Study): A Prospective Study Protocol

Introduction: Fever of unknown origin (FUO) and hemodynamic instability are complications that develop after cardiac surgery combined with cardiopulmonary bypass (CPB) for heart disease. Patients who develop fever with hemodynamic instability after cardiac surgery may have systemic inflammatory response syndrome or sepsis. Cardiopulmonary bypass (CPB) is a technique that temporarily takes over the function of the heart and lungs during cardiac surgery. Recent reports suggest that early bloodstream infections of patients undergoing CPB are due to gram-negative bacteria that are present in the intestinal flora. The theory of intestinal flora translocation has growing evidence. Intestinal ischemia-reperfusion that occurs during cardiac surgery with CPB will induce a systemic inflammatory reaction and may cause intestinal flora translocation. Does this systemic reaction cause sepsis? We therefore propose this protocol to determine whether the changes in the intestinal flora in patients after cardiac surgery with CPB are related to sepsis. Methods and Analysis: This study is a prospective observational case-control study to analyze the variation in the intestinal microflora and metabolites in patients undergoing cardiac surgery with CPB and to observe the outcomes of patients with routine clinical interventions. The control group will include healthy people without intestinal illness. Feces and blood samples will be acquired 1 day before cardiac surgery and within 24-72 h after cardiac surgery, and will be used for genomics and metabolomics analyses. Demographic data describing age, sex, main diagnosis, and past medical history and data related to the CPB time and application of antibiotics are available. Sequential (sepsis-related) organ failure assessment, infection-related laboratory items, infection site, and pathogenic microorganisms, and nutrition, and gastrointestinal function assessment are additionally recorded. Group analysis of data will be conducted according to the outcomes (sepsis vs. non-sepsis and survivors vs. non-survivors). Ethics and Dissemination: This protocol has been ethically approved by the Ethics Committee of Peking Union Medical College (ID: ZS-1612). Informed consent will be obtained before subject enrolment, and data will be stored in a secured database. The results will be submitted to international peer-reviewed journals and presented at international conferences. Trial Registration Number: NCT04032938.

Total Body Irradiation Mitigates Inflammation and Extends the Therapeutic Time Window for Anti-Ricin Antibody Treatment against Pulmonary Ricinosis in Mice

Ricin, a highly toxic plant-derived toxin, is considered a potential weapon in biowarfare and bioterrorism due to its pronounced toxicity, high availability, and ease of preparation. Pulmonary exposure to ricin results in the generation of an acute edematous inflammation followed by respiratory insufficiency and death. Massive neutrophil recruitment to the lungs may contribute significantly to ricin-mediated morbidity. In this study, total body irradiation (TBI) served as a non-pharmacological tool to decrease the potential neutrophil-induced lung injury. TBI significantly postponed the time to death of intranasally ricin-intoxicated mice, given that leukopenia remained stable following intoxication. This increase in time to death coincided with a significant reduction in pro-inflammatory marker levels, and led to marked extension of the therapeutic time window for anti-ricin antibody treatment.

Overexpression of Brg1 Alleviates Hepatic Ischemia/Reperfusion-Induced Acute Lung Injury through Antioxidative Stress Effects

AIM

To investigate whether overexpression of Brahma-related gene-1 (Brg1) can alleviate lung injury induced by hepatic ischemia/reperfusion (HIR) and its precise mechanism.

METHODS

Cytomegalovirus-transgenic Brg1-overexpressing (CMV-Brg1) mice and wild-type (WT) C57BL/6 mice underwent HIR. Lung histology, oxidative injury markers, and antioxidant enzyme concentrations in the lung were assessed. The protein expression levels of Brg1, nuclear factor erythroid 2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1), and NAD(P)H:quinone oxidoreductase 1 (NQO1) in the lung were analyzed by Western blotting.

RESULTS

In the WT group, histopathological analysis revealed that lung damage peaked at 6 h after HIR. Meanwhile, the lung reactive oxygen species (ROS) and 8-isoprostane levels were significantly increased. The protein expression of Brg1 in lung tissue decreased to a minimum at 6 h. Overexpression of Brg1 alleviated lung injury and decreased the amounts of oxidative products, including the levels of 8-isoprostane and ROS, as well as the percentage of positive cells for 4-hydroxynonenal (4-HNE) and 8-oxo-2'-deoxyguanosine (8-OHdG). Brg1 overexpression increased the expression and nuclear translocation of Nrf2 as well as activated the antioxidases. In addition, it decreased the expression of inflammatory factors.

CONCLUSION

Overexpression of Brg1 alleviates oxidative lung injury induced by HIR, likely through the Nrf2 pathway.

Potent Antiedematous and Protective Effects of Ciprofloxacin in Pulmonary Ricinosis

The plant toxin ricin is considered a biological threat agent of concern and is most toxic when inhaled. Pulmonary exposure to a lethal dose of ricin can be redressed by treatment with antiricin antibodies; however, late antitoxin intervention is of limited efficacy. This limitation is associated with overt lung damage, clinically manifested as severe pulmonary inflammation, which develops over time. Increased evidence indicates that ciprofloxacin, a broad-spectrum antimicrobial agent, possesses immunomodulatory properties. Here we demonstrate that while antiricin antibody administration at late hours after intranasal exposure to ricin confers limited protection to mice, highly efficient protection can be achieved by adding ciprofloxacin to the antibody treatment. We further demonstrate that parameters associated with lung injury, in particular, pulmonary proinflammatory cytokine production, neutrophil migration, and edema, are sharply reduced in ricin-intoxicated mice that were treated with ciprofloxacin. The presented data highlight the potential clinical application of ciprofloxacin as a beneficial immunomodulatory agent in the course of ricin intoxication.

The effect of antioxidant supplementation on bacterial translocation after intestinal ischemia and reperfusion

The intestine is highly sensitive to ischemia/reperfusion (I/R) injury. Intestinal I/R may cause local tissue injury and disruption of the intestinal mucosal barrier, allowing the passage of viable bacteria and endotoxins from the gastrointestinal lumen to distant organs. This phenomenon, known as bacterial translocation (BT), may lead to systemic disorders with high morbidity and mortality. Oxidative stress mediators such as reactive oxygen species, polymorphonuclear neutrophils and nitric oxide are believed to contribute to the intestinal I/R injury. Many antioxidants have shown protective effects against I/R injury of various organs. The present article provides an overview of studies investigating the effect of antioxidant supplementation on BT after intestinal I/R.

Abdominal paracentesis drainage protects rats against severe acute pancreatitis-associated lung injury by reducing the mobilization of intestinal XDH/XOD

Our previous study showed that abdominal paracentesis drainage (APD) benefits patients with severe acute pancreatitis (SAP) by delaying or avoiding multiple organ failure. However, the role of APD treatment in SAP-associated lung injury (PALI) remains unclear. Therefore, we investigated the impact of APD on PALI in rats to explore the mechanisms underlying its potential treatment benefits. A drainage tube was inserted into the right lower quadrant of rats immediately after SAP induction via the retrograde infusion of 5% sodium taurocholate into the biliopancreatic duct. Mortality rates, histological scores, wet-to-dry weight (W/D) ratios, inflammatory infiltration and oxidative stress in lung tissues were then examined. Xanthine dehydrogenase (XDH) and xanthine oxidase (XOD) activities in the sera, intestines and lungs were assessed, as was P-selectin expression. APD treatment significantly decreased pathological damage scores, oxidative stress and neutrophil infiltration in lung tissues, indicating that APD has protective effects against PALI in rats. Moreover, APD decreased the levels of serum α-amylase and trypsin and resulted in a significant decrease in XDH mobilization from the intestines, which suppressed P-selectin expression in lung tissues following SAP induction. APD treatment exerts a significant protective effect against lung injury secondary to SAP by reducing the mobilization of intestinal XDH or XOD (XDH/XOD) and the expression of P-selectin in the lungs. These findings provide novel insights into the mechanisms underlying the effectiveness of APD in patients with SAP.

Febuxostat protects rats against lipopolysaccharide-induced lung inflammation in a dose-dependent manner

The aim of the present work was to investigate possible protective effects of febuxostat, a highly potent xanthine oxidase inhibitor, against acute lung injury (ALI) induced by lipopolysaccharide (LPS) in rats. Male Sprague Dawley rats were randomly divided into six groups, as follows: (i) vehicle control group; (ii) and (iii) febuxostat 10 and febuxostat 15 groups, drug-treated controls; (iv) LPS group, receiving an intraperitoneal injection of LPS (7.5 mg/kg); (v) and (vi) febuxostat 10-LPS and febuxostat 15-LPS groups, receiving oral treatment of febuxostat (10 and 15 mg/kg/day, respectively) for 7 days before LPS. After 18 h administration of LPS, blood was collected for C-reactive protein (CRP) measurement. Bronchoalveolar lavage fluid (BALF) was examined for leukocyte infiltration, lactate dehydrogenase (LDH) activity, protein content, and total nitrate/nitrite. Lung weight gain was determined, and lung tissue homogenate was prepared and evaluated for oxidative stress. Tumor necrosis factor-α (TNF-α) was assessed in BALF and lung homogenate. Moreover, histological changes of lung tissues were evaluated. LPS elicited lung injury characterized by increased lung water content (by 1.2 fold), leukocyte infiltration (by 13 fold), inflammation and oxidative stress (indicated by increased malondialdehyde (MDA), by 3.4 fold), and reduced superoxide dismutase (SOD) activity (by 34 %). Febuxostat dose-dependently decreased LPS-induced lung edema and elevations in BALF protein content, infiltration of leukocytes, and LDH activity. Moreover, the elevated levels of TNF-α in BALF and lung tissue of LPS-treated rats were attenuated by febuxostat pretreatment. Febuxostat also displayed a potent antioxidant activity by decreasing lung tissue levels of MDA and enhancing SOD activity. Histological analysis of lung tissue further demonstrated that febuxostat dose-dependently reversed LPS-induced histopathological changes. These findings demonstrate a significant dose-dependent protection by febuxostat against LPS-induced lung inflammation in rats.

Edaravone prevents lung injury induced by hepatic ischemia-reperfusion

BACKGROUND

Lung injury is a major clinical concern after hepatic ischemia-reperfusion (I/R), due to the production of reactive oxygen species in the reperfused liver. We investigated the efficacy of edaravone, a potent free-radical scavenger, for attenuating lung injury after hepatic I/R.

MATERIALS AND METHODS

Adult male Sprague-Dawley rats were assigned to sham + normal saline (NS), I/R + NS, or I/R + edaravone group. Rats in the I/R groups were subjected to 90 min of partial hepatic I/R. Five minutes before reperfusion, 3 mg/kg edaravone was administered to the I/R + edaravone group. After 6 h of reperfusion, we evaluated lung histopathology and wet-to-dry ratio. We also measured malondialdehyde (MDA), an indicator of oxidative stress, in the liver and the lung, as well as cytokine messenger RNA expressions in the reperfused liver and plasma cytokine concentrations.

RESULTS

Histopathology revealed lung damages after 6 h reperfusion of partial ischemic liver. Moreover, a significant increase in lung wet-to-dry ratio was observed. MDA concentration increased in the reperfused liver, but not in the lungs. Edaravone administration attenuated the lung injury and the increase of MDA in the reperfused liver. Edaravone also suppressed the reperfusion-induced increase of interleukin-6 messenger RNA expressions in the liver and plasma interleukin-6 concentrations.

CONCLUSIONS

Edaravone administration before reperfusion of the ischemic liver attenuates oxidative stress in the reperfused liver and the subsequent lung injury. Edaravone may be beneficial for preventing lung injury induced by hepatic I/R.

Global consequences of liver ischemia/reperfusion injury

Liver ischemia/reperfusion injury has been extensively studied during the last decades and has been implicated in the pathophysiology of many clinical entities following hepatic surgery and transplantation. Apart from its pivotal role in the pathogenesis of the organ's post reperfusion injury, it has also been proposed as an underlying mechanism responsible for the dysfunction and injury of other organs as well. It seems that liver ischemia and reperfusion represent an event with “global” consequences that influence the function of many remote organs including the lung, kidney, intestine, pancreas, adrenals, and myocardium among others. The molecular and clinical manifestation of these remote organs injury may lead to the multiple organ dysfunction syndrome, frequently encountered in these patients. Remote organ injury seems to be in part the result of the oxidative burst and the inflammatory response following reperfusion. The present paper aims to review the existing literature regarding the proposed mechanisms of remote organ injury after liver ischemia and reperfusion.

Xanthine oxidase inhibitory activities of extracts and flavonoids of the leaves of Blumea balsamifera

CONTEXT

Blumea balsamifera DC (Compositae) leaves have been recommended for use as a folk medicine in the treatment of various diseases related to urolithiasis in southeast Asia. Phytochemical studies of this plant revealed it contains four classes of flavonoids (e.g., flavonols, flavones, flavanones, and dihydroflavonol derivatives).

OBJECTIVE

In view of the broad pharmacological activity of flavonoids, this study was carried out to determine the xanthine oxidase (XO) inhibitory and enzymatically produced superoxide radical scavenging activity of different organic extracts and that of the isolated flavonoids from B. balsamifera leaves.

MATERIALS AND METHODS

The inhibitory activity of XO was assayed spectrophotometrically at 295 nm. The superoxide radicals scavenging activity was assessed by NBT reduction method, spectrophotometrically at 560 nm. A dose response curve was plotted for determining IC₅₀ values.

RESULTS

The methanol extract (IC₅₀ = 0.111 mg/mL) showed higher XO inhibitory activity than the chloroform (0.138 mg/mL) and pet-ether extracts (0.516 mg/mL). IC₅₀ values of scavenging of superoxide radicals for extracts decreased in the order of: methanol (0.063 mg/mL) > chloroform (0.092 mg/mL) > pet-ether (0.321 mg/mL). The XO inhibitory activity of the isolated flavonoids and reference compounds tested decreased in the order of: allopurinol > luteolin > quercetin > tamarixetin > 5,7,3',5'-tetrahydroxyflavanone > rhamnetin > luteolin-7-methyl ether > blumeatin > dihydroquercetin-4'-methyl ether > dihydroquercetin-7,4'-dimethyl ether > L-ascorbic acid.

DISCUSSION AND CONCLUSION

The results indicated that the flavone derivatives were more active than the flavonol derivatives. The flavanone derivatives were moderately active and the dihydroflavonol derivatives were the least. The higher flavonoid content of extracts contributed to their higher XO inhibitory activity.

Methylene blue attenuates pancreas ischemia-reperfusion (IR)-induced lung injury: a dose response study in a rat model

BACKGROUND

Oxidants (and their generator, xanthine oxidase [XO]) play a role in inducing acute lung injury (ALI) expressed both structurally and functionally. Such damage has recently been demonstrated in the presence of pancreas ischemia-reperfusion (IR). We now investigated whether methylene blue (MB), a clinically used coloring agent and antioxidant in itself, protected the lung exposed to pancreas IR.

MATERIALS AND METHODS

Isolated pancreata (eight replicates/group) were (1) continuously perfused (controls), (2) made ischemic (IR-0) for 40 min and reperfused without treatment, (3) organs procured from allopurinol-treated rats made ischemic and reperfused with allopurinol, and (4) made ischemic and treated upon reperfusion with three different doses of MB contained in the perfusate. All perfusate solutions were directed into the isolated lungs' circulation whereby they were perfused for 60 min.

RESULTS

Pancreas injury was documented in all IR organs by abnormally high reperfusion pressure, wet-to-dry ratio, amylase and lipase concentrations, and abnormal XO activity and reduced glutathione in the circulation. Lungs paired with IR-0 pancreata developed approximately 60% increase in ventilatory plateau pressure and final PO(2)/FiO(2) decrease by 35%. Their weight during reperfusion and bronchoalveolar lavage (BAL) volume and contents increased 1.5-2.5 times the normal values; XO and reduced glutathione values were abnormal both in the BAL and in the lung tissues. Lungs exposed to IR effluents containing allopurinol or 68 microM MB were minimally damaged, whereas perfusion solutions containing 42 or 128 microM MB were ineffective in preventing lung injury.

CONCLUSIONS

Ex vivo pancreas IR-induced ALI is preventable by MB, although at a narrow dose range.

Mannitol prevents acute lung injury after pancreas ischemia-reperfusion: a dose-response, ex vivo study

Oxidants and their generator, xanthine oxidase (XO), play a major role in the damaging of the structural and functional integrity of the lung. Such damage has been recently demonstrated in the presence of pancreas ischemia-reperfusion (IR). We investigated whether mannitol, a clinically used agent and antioxidant, prevented lung damage after pancreas IR. Rats (n = 48) were anesthetized, after which each pancreas was isolated and perfused (controls), or made ischemic (IR) for 40 min, or made ischemic and treated upon reperfusion with four different doses of mannitol administered in the perfusate (8 replicates/group). Ischemia was followed by in-series 15-min pancreas plus normal isolated lung reperfusion. Isolated lungs were subsequently perfused for 45 min with the 15-min accumulated effluents. Pancreas injury occurred in all IR organs as demonstrated by abnormal reperfusion pressure, the wet-to-dry ratio, amylase and lipase leakage into the circulation, and XO activity and reduced glutathione (GSH) pool in the tissues. Pulmonary plateau pressure increased by 80%, and final PO(2)/FiO(2) decreased by 28% in the IR-untreated paired lungs. Bronchoalveolar lavage volume increased by 50% and 2- to 8-fold increase in their contained XO and GSH were recorded as well. The above indices of injury in lungs perfused with 0.77 mM mannitol were the least detected, compared with negligible efficacy of other (0.55 < 0.22 < 1.1 mM) dosages. Amylase and lipase did not contribute to lung injury. Ex vivo acute pancreatitis induces acute lung injury via oxidants/antioxidants imbalance, which is preventable by mannitol.

Propofol attenuates the decrease of dynamic compliance and water content in the lung by decreasing oxidative radicals released from the reperfused liver

BACKGROUND

Remote pulmonary injuries after hepatic reperfusion are frequently caused by reactive oxygen species (ROS)-induced damage. The choice of anesthetics may affect the balance between oxidants and antioxidants, and propofol, a commonly used anesthetic, has an antioxidant effect. In this study, we developed a model to study pulmonary function with hepatic ischemia/reperfusion (I/R) manipulation, with the aim of defining remote pulmonary dysfunction after hepatic reperfusion and determining if propofol affects this dysfunction by altering ROS production from the liver or lungs.

METHODS

Adult male rats weighing 160-250 g were randomly divided into four groups according to the type of surgery (sham or I/R) and the anesthetic administered (pentobarbital or propofol). To induce I/R, the portal vein and hepatic artery to the left and medial lobes of the liver were clamped. All of the measurements were done after 5 h of reperfusion, after 45 min of ischemia. Pulmonary function after hepatic I/R was determined by dynamic compliance, resistance and wet-to-dry ratio, and by histopathology. Hepato-cellular injuries were confirmed by alanine aminotransferase, whereas ROS production was measured from the inferior vena cava, jugular vein, and carotid artery. Products of lipid peroxidation, thiobarbiturate acid reactive substances and malondialdehyde, were measured in lung and hepatic tissues.

RESULTS

Remote lung injury after hepatic I/R was shown by a significant decrease of Cdyn, and increases in resistance and the wet-to-dry ratio. ROS production was significantly increased and was highest in samples from the inferior vena cava. Thiobarbiturate acid reactive substances and malondialdehyde in the liver and serum alanine aminotransferase were significantly increased only in the I/R+pentobarbital group. All of the changes were significantly attenuated in the I/R+ propofol group (P=0.05). With propofol infusion, there was decreased ROS production from the reperfused liver, with less hepato-cellular injury, followed by well-maintained pulmonary function.

CONCLUSION

Remote pulmonary dysfunction and reperfusion injury in the liver were demonstrated in our rat model, as well as massive ROS production and lipid peroxidation. Propofol infusion attenuated remote pulmonary injury by lessening oxidative injury from the reperfused liver.

Moderate hypothermia as a rescue therapy against intestinal ischemia and reperfusion injury in the rat

OBJECTIVE

Moderate hypothermia is protective when applied throughout experimental intestinal ischemia and reperfusion (I/R). However, therapeutic intervention is usually possible only after ischemia has occurred. The aim of this study was to evaluate moderate hypothermia when applied at reperfusion as a rescue therapy for intestinal I/R.

DESIGN

Prospective, randomized, controlled experiment.

SETTING

University research laboratory.

SUBJECTS

Adult male Sprague-Dawley rats (240-300 g).

INTERVENTIONS

In experiment I, rats underwent 60 mins of normothermic intestinal ischemia (36-38 degrees C) plus 300 mins of reperfusion at either normothermia or moderate hypothermia (30-32 degrees C) with or without rewarming. Hemodynamics were measured invasively and survival was assessed. In experiment II, rats underwent 60 mins of normothermic ischemia plus 120 mins of reperfusion at either normothermia or moderate hypothermia. At kill, organs and a blood sample were collected.

MEASUREMENTS AND MAIN RESULTS

In experiment I, all normothermic I/R rats died within 197 mins of reperfusion after developing severe tachycardia and hypotension, whereas hypothermic rats, with or without rewarming, were alive at 300 mins of reperfusion (p < .001 vs. I/R normothermia) and were hemodynamically stable. In experiment II, normothermic reperfusion caused histologic and biochemical damage to the gut, hepatic energy failure, and inflammatory infiltration of the lung. However, hypothermia reduced injury to the reperfused ileum and prevented distant organ injury by counteracting energy failure in the liver, systemic overproduction of nitric oxide, altered cardiac fatty acid metabolism, and infiltration of inflammatory cells in the lungs.

CONCLUSIONS

Hypothermia applied as a rescue therapy for intestinal I/R abolishes mortality even after rewarming. Hypothermic protection during early reperfusion appears to be mediated by several pathways, including prevention of intestinal and pulmonary neutrophil infiltration, reduction of oxidative stress in the ileum, and preservation of cardiac and hepatic energy metabolism. Moderate hypothermia may improve outcome in clinical conditions associated with intestinal I/R.

Impact of cold preservation on leukocyte adhesion to the transplanted rat lung

Little is known about leukocyte migration in the early phase after ischemia-reperfusion injury. Recently, there has been much focus on in vivo visualization of cell kinetics. Previously, we established a method for the in vivo visualization of leukocyte circulation using a Green Fluorescent Protein transgenic rat. Herein, we developed a simplified rat heterotopic lung transplantation model that can be mastered by beginners within a few weeks. Using this system, we studied the impact of preservation on adhesion of circulating leukocytes to the transplanted lung. The graft of a fresh group was compared with that of a preserved group. Morphological and immunohistochemical analyses were also performed. We successfully visualized few adherent leukocytes in the fresh graft, whereas adherent cells were attached in the preserved graft within a few minutes. In conclusion, the prolonged cold preservation time promotes leukocyte adhesion, resulting in increased microvascular injury after lung transplantation.

Effects of preoperative flavonoid supplementation on different organ functions in rats

BACKGROUND

Previously it has been reported that preoperative feeding preserves heart function in rats after intestinal ischemia-reperfusion. To further improve postoperative organ function, bioactive nutrition compounds were selected in vitro against the xanthine oxidase radical cascade, an enzyme suggested to play a key role in the induction of single- or multiple-organ dysfunction.

METHODS

Flavonoids were selected in vitro for their capacity to (1) inhibit xanthine oxidase, (2) scavenge superoxide, and (3) scavenge peroxylradicals. The most bioactive flavonoids were added to the preoperative nutrition to study their effect on postintestinal ischemia-reperfusion organ function.

RESULTS

A combination of flavonoids selected on basis of effective flavonoid xanthine oxidase inhibition and superoxide scavenging resulted in increased superoxide scavenging. In vivo, the selected flavonoid mixture significantly lowered postischemic intestinal apoptosis and intestinal oxidative stress indicated by malondialdehyde concentration when compared with ischemia-reperfusion fasted and sham-fasted animals. Moreover, this flavonoid mixture significantly lowered plasma creatinine and urea concentration, both indicating a better postoperative kidney function. Furthermore, oxidative stress measured as this flavonoid mixture when compared with control significantly lowered plasma malondialdehyde concentration in fed rats.

CONCLUSIONS

Coadministration of bioactive flavonoid mixture to preoperative nutrition, in contrast to fasting, attenuates ischemia-reperfusion injury by preserving kidney function in the rat and decreasing apoptosis in the intestine.

Acute lung injury following pancreas ischaemia-reperfusion: role of xanthine oxidase

BACKGROUND

Acute pancreatitis can lead to increased pulmonary vascular permeability and respiratory failure. Oxidants (and their generator, xanthine oxidase (XO)) play an important role in injuring the structural integrity of the pulmonary epithelium and endothelium, but their importance in the induction of acute lung injury following pancreas ischaemia-reperfusion (IR) has not been defined.

MATERIALS AND METHODS

Rats (n = 48) received a regular or a tungsten (oxidoreductase inhibitor)-enriched diet for 14 days. Their isolated pancreases were then either perfused (controls) or made ischaemic (IR) for 40 min (12 replicates/group). This was followed by in-series pancreas plus normal isolated lung reperfusion for 15 min. Lungs only were subsequently perfused with the 15-min accumulated pancreas effluents for 45 min.

RESULTS

Injury was induced in all IR pancreases as expressed by reperfusion pressure, wet-to-dry ratio and amylase and lipase concentrations. Tissue XO activity was high and reduced glutathione pool was low in the tungsten-free IR pancreases. Pulmonary plateau pressure increased by 46% and final PO(2)/FiO(2) decreased by 24%. Capillary pressure and weight rose two- to fourfold in lungs paired with IR non-treated pancreases. Twofold increases in bronchoalveolar lavage volume and contents, including XO, were also recorded in this group of lungs. Lungs exposed to tungsten-treated ischaemic pancreas effluents were minimally damaged and tissue XO content was low compared to controls.

CONCLUSIONS

Ex-vivo acute pancreatitis induces acute lung injury via oxidants/antioxidants misbalance, which may be prevented by attenuating pancreas oxidative stress.

Shen-Fu attenuates endotoxin-induced acute lung injury in rats

Sepsis is associated with the highest risk of progression to acute lung injury or acute respiratory distress syndrome. Shen-Fu has been advocated to treat many severely ill patients. Our study was designed to investigate the effect of Shen-Fu on endotoxin-induced acute lung injury in vivo. Adult male Wistar rats were randomly divided into 6 groups: controls; those challenged with endotoxin (5 mg/kg) and treated with saline; those challenged with endotoxin (5 mg/kg) and treated with Shen-Fu (1 mg/kg); those challenged with endotoxin (5 mg/kg) and treated with Shen-Fu (10 mg/kg); increase challenged with endotoxin (5 mg/kg) and treated with Shen-Fu (100 mg/kg); saline injected and treated with Shen-Fu (100 mg/kg). TNF-alpha, IL-6, and NF-kappa B were investigated in the lung two hours later. Myeloperoxidase (MPO) activity and wet/dry weight ratio were investigated six hours later. Intravenous administration of endotoxin provoked significant lung injury, which was characterized by increment increase of MPO activity and wet/dry lung weight ratio, and TNF-alpha and IL-6 expression and NF-kappa B activation. Shen-Fu (10,100 mg/kg) decreased MPO activity and wet/dry weight ratio and inhibited TNF-alpha and IL-6 production, endotoxin-induced NF-kappa B activation. Our results indicated that Shen-Fu at a dose of higher than 10 mg/kg inhibited endotoxin-induced pulmonary inflammation in vivo.

Lung oxidative stress as related to exercise and altitude. Lipid peroxidation evidence in exhaled breath condensate: a possible predictor of acute mountain sickness

Lung oxidative stress (OS) was explored in resting and in exercising subjects exposed to moderate and high altitude. Exhaled breath condensate (EBC) was collected under field conditions in male high-competition mountain bikers performing a maximal cycloergometric exercise at 670 m and at 2,160 m, as well as, in male soldiers climbing up to 6,125 m in Northern Chile. Malondialdehyde concentration [MDA] was measured by high-performance liquid chromatography in EBC and in serum samples. Hydrogen peroxide concentration [H(2)O(2)] was analysed in EBC according to the spectrophotometric FOX(2) assay. [MDA] in EBC of bikers did not change while exercising at 670 m, but increased from 30.0+/-8.0 to 50.0+/-11.0 nmol l(-1) (P<0.05) at 2,160 m. Concomitantly, [MDA] in serum and [H(2)O(2)] in EBC remained constant. On the other hand, in mountaineering soldiers, [H(2)O(2)] in EBC under resting conditions increased from 0.30+/-0.12 mumol l(-1) at 670 m to 1.14+/-0.29 mumol l(-1) immediately on return from the mountain. Three days later, [H(2)O(2)] in EBC (0.93 +/-0.23 mumol l(-1)) continued to be elevated (P<0.05). [MDA] in EBC increased from 71+/-16 nmol l(-1) at 670 m to 128+/-26 nmol l(-1) at 3,000 m (P<0.05). Changes of [H(2)O(2)] in EBC while ascending from 670 m up to 3,000 m inversely correlated with concomitant variations in HbO2 saturation (r=-0.48, P<0.05). AMS score evaluated at 5,000 m directly correlated with changes of [MDA] in EBC occurring while the subjects moved from 670 to 3,000 m (r=0.51, P<0.05). Lung OS may constitute a pathogenic factor in AMS.

Hypocapnia attenuates mesenteric ischemia-reperfusion injury in a rat model

PURPOSE

Hypocapnia, a recognized complication of high frequency oscillation ventilation, has multiple adverse effects on lung and brain physiology in vivo, including potentiation of free radical injury. We hypothesized that hypocapnia would potentiate the effects of mesenteric ischemia-reperfusion on bowel, liver and lung injury.

METHODS

Anesthetized male Sprague-Dawley rats were ventilated with high frequency oscillation and were randomized to one of four groups, exposed to either mesenteric ischemia-reperfusion or sham surgery, and to either hypocapnia or normocapnia.

RESULTS

All animals survived the protocol. Ischemia-reperfusion caused significant histologic bowel injury. Bowel 8-isoprostane generation was greater in ischemia-reperfusion vs sham, but was attenuated by hypocapnia. Laser-Doppler flow studies of bowel perfusion confirmed that hypocapnia attenuated reperfusion following ischemia. Plasma alanine transaminase, reflecting overall hepatocellular injury, was not increased by ischemia-reperfusion but was increased by hypocapnia; however, hepatic isoprostane generation was increased by ischemia-reperfusion, and not by hypocapnia. Oxygenation was comparable in all groups, and compliance was impaired by ischemia-reperfusion but not by hypocapnia.

CONCLUSION

Hypocapnia, although directly injurious to the liver, attenuates ischemia-reperfusion induced lipid peroxidation in the bowel, possibly through attenuation of blood flow during reperfusion.

SIVELESTAT, A NEUTROPHIL ELASTASE INHIBITOR, ATTENUATES NEUTROPHIL PRIMING AFTER HEPATOENTERIC ISCHEMIA IN RABBITS

Neutrophils play an important role in ischemia-reperfusion injury. The neutrophil elastase not only causes tissue damage, but also mediates neutrophil priming. In the present study, we use a rabbit model of hepatoenteric ischemia-reperfusion to test the hypothesis that neutrophil elastase inhibition ameliorates an ischemia-reperfusion injury by attenuating neutrophil priming and suppressing enzymatic activity. Twenty-four Japanese white rabbits underwent 30 min of supraceliac aortic cross-clamping and 180 min of reperfusion under isoflurane anesthesia. The rabbits randomly received the neutrophil elastase inhibitor, sivelestat (n = 10), or saline (n = 14). Neutrophil priming was then assayed with luminol-dependent neutrophil chemiluminescence. Hepatic, intestinal, renal, and pulmonary damages were assessed with serum transaminase, lactate dehydrogenase concentrations, urinary N-acetyl glucosaminidase activity, and protein concentration in post mortem bronchoalveolar lavage fluid. We discovered that neutrophil elastase inhibition suppressed plasma neutrophil elastase, and that lipid peroxide concentrations increased after reperfusion. It improved ischemia-reperfusion injuries in the liver, intestine, kidney, and lung. Furthermore, inhibition of neutrophil elastase with sivelestat significantly attenuated post-reperfusion neutrophil priming. The results of this study demonstrate that neutrophil elastase inhibition could effectively attenuate an ischemia-reperfusion injury caused by supraceliac aortic cross-clamping, most likely from the attenuation of neutrophil priming.

Pulmonary MnSOD Is Nitrated Following Hepatic Ischemia-Reperfusion

BACKGROUND

Ischemia-reperfusion (I/R) of remote organs is a common cause of lung injury. We observed that lung injury after partial hepatic I/R in mice coincides with the appearance of 3-nitrotyrosine (NT) in the lung tissue, a marker of peroxynitrite involvement and oxidant stress. Peroxynitrite can cause mitochondrial dysfunction by inactivation of manganese superoxide dismutase (MnSOD), the major antioxidant enzyme in mitochondria. Our aims were to examine whether pulmonary MnSOD is a target of nitration following hepatic I/R and whether nitrated MnSOD (N-MnSOD) correlates with acute lung injury.

METHODS

Five 20-25-g male C57BL/6 mice underwent laparotomy, and atraumatic occlusion of the portal and arterial blood supply to the upper three lobes of the liver for 90 min. This warm ischemic period was followed by 4 h of reperfusion, and the animals were then euthanized. Lung injury was assessed by LDH and protein levels in bronchoalveolar lavage (BAL) fluid. Pulmonary MnSOD activity in pulmonary homogenates was measured by the cytochrome c reduction method. The presence of N-MnSOD was determined by immunoprecipitation (IP) and Western Blot analysis. Controls (N = 5) underwent sham operation.

RESULTS

Elevated plasma transaminases confirmed hepatic injury. Lung injury was demonstrated by elevation in BAL protein and LDH levels (495.7 (48.4) versus 644.9 (37.3) [p < 0.05] and 56.5 (11.8) versus 345.2 (80) [p < 0.01], respectively). Immunoprecipitation and Western blot demonstrated N-MnSOD in the lung tissue of I/R animals but not controls. MnSOD activity decreased following I/R (8.1 (0.7) versus 10.8 (0.3) [p < 0.05]).

CONCLUSIONS

Pulmonary MnSOD is both nitrated and inactivated following hepatic I/R and is associated with acute lung injury. These findings suggest that MnSOD incapacitance may contribute to I/R-induced lung injury and provide a therapeutic target in attenuating multisystem injury following hepatic I/R.

Alteration of soluble adhesion molecules during aging and their modulation by calorie restriction

To investigate the status of soluble adhesion molecules (sAMs) during aging, the present study determined protein levels of several major sAMs in serum samples obtained from rats at different ages. These sAMs include E-selectin, P-selectin, vascular cell adhesion molecule 1 (VCAM-1), and intercellular adhesion molecule 1 (ICAM-1). Fischer 344 rats, ages 6, 12, 18, and 24 months, fed ad libitum (AL) and calorie restricted (CR) diets were used in this study. Analysis by Western blotting showed that the levels of all sAMs studied increased during aging in AL rats, but were effectively blunted in the CR rats. Total reactive oxygen species/reactive nitrogen species (ROS/RNS) levels were measured by fluorescent probe 2',7'-dichlorofluorescin diacetate. Increased ROS/RNS levels were found to coincide with increased levels of superoxide-generating xanthine oxidase in serum during aging, but were found suppressed by CR. Increases in sAMs levels were duplicated in another experiment in which young (13-month-old) and old (31-month-old) rats were injected with proinflammatory lipopolysaccharide. These findings suggest that the altered expressions of sAMs may be due to increased oxidative stress with advanced age and that these increases were prevented by CR through its antioxidative action.

Coagulopathy mediated by hepatoenteric ischemia-reperfusion in rabbits: role of xanthine oxidase

Hepatic transplantation may result in coagulopathy caused by the release of mast-cell-derived heparin, and xanthine oxidase (XO) inhibition stabilizes mast cells. Thus, XO inactivation could decrease coagulopathy after hepatoenteric ischemia-reperfusion. Rabbits were fed a standard or XO-inactivating diet before hepatoenteric ischemia for 35 min and before 30 min of reperfusion. Hemostasis was assessed by thrombelastography. Heparin activity was quantified by anti-IIa. XO inactivation resulted in clot formation after reperfusion in all animals, whereas only 37.5% of animals with XO activity clotted (P<0.05). Anti-IIa activity was less in animals at baseline and after reperfusion with XO inactivation (45+/-5 and 65+/-5 mU/mL, respectively) compared to animals with XO activity (51+/-4 and 71+/-5 mU/mL, respectively) (P<0.05). Clot strength, which was mediated by coagulation proteins, was significantly greater at baseline and after reperfusion in animals with XO inactivation. XO inactivation enhances hemostasis by decreasing circulating heparin activity and increasing coagulation protein function before ischemia-reperfusion.

Accurate prediction of xanthine oxidase inhibition based on the structure of flavonoids

The flavonoid family shows a high potential for inhibition of xanthine oxidase. Currently, more than 4,000 flavonoids are known. The data of this study indicate that a planar structure is necessary for high inhibitory activity towards xanthine oxidase. Moreover, the contribution of a hydroxyl conjugate turns out to be a constant factor when the natural logarithm of IC(50) values is taken. This finding allows us to accurately predict the IC(50) value of any given hydroxyl group added to the basic flavone structure towards xanthine oxidase. This new method may provide an important research tool for elucidating the role that flavonoids may have in radical related diseases.

Global effects of xanthine oxidase stress on alveolar type II cells

OBJECTIVE: To delineate biochemical details of graded xanthine oxidase stress toward cultured alveolar type II cells, particularly oxidant-mediated damage of type II cell nucleic acid, protein, and lipid, as an in vitro model of distant ischemia-reperfusion lung injury. DESIGN: In vitro injury model using native rat and immortalized mouse alveolar type II cells and exogenous xanthine oxidase. SETTING: Research laboratory. Measurement: Cultured type II cells were subjected to xanthine oxidase-derived reactive oxygen stress at variable concentrations and incubation times. Reduction of type II cell double-stranded DNA, inhibition of de novo phosphatidyl choline synthesis, enhancement of lipid peroxidation, and suppression of mitochondrial redox capacity were analyzed in relation to high-intensity (xanthine oxidase, 25 munits/mL) oxidant stress. Alterations in type II cell cellular glutathione-related antioxidant repertoire were assessed at both high-intensity and low-intensity (xanthine oxidase, 1 munits/mL) oxidant stress. MAIN RESULTS: High-intensity xanthine oxidase stress significantly increased type II cell DNA strand breakage, inhibited de novo phosphatidyl choline synthesis, diminished mitochondrial integrity, and enhanced lipid peroxidation in the absence of overt cytolysis. This injury was modulated with addition of exogenous glutathione peroxidase, or catalase/superoxide dismutase, but not glutathione or N-acetylcysteine. Although aspects of the glutathione antioxidant repertoire were similarly diminished with high-intensity xanthine oxidase stress, low-dose (long duration) xanthine oxidase stress augmented the activities of type II cell glutathione peroxidase and gamma-glutamyl transferase (the rate-limiting enzyme in glutathione synthesis). CONCLUSION: High-intensity xanthine oxidase stress (in vitro model of in vivo ischemia-reperfusion) may overwhelm type II cell antioxidant defenses and mediate oxidant injury to nucleic acid, protein, and lipid in the absence of cell lysis. Immortalized murine type II cells seem to appropriately model xanthine oxidase-mediated nucleic acid and protein injury of native rat type II cells. Exogenous glutathione peroxidase reduces oxidant injury in this in vitro model. Depending on magnitude (and possibly duration) of the xanthine oxidase stress, type II cell glutathione antioxidant elements may be diminished or enhanced.

Efeito da N-acetilcisteína no pulmão após isquemia hepática em ratos

Na síndrome de isquemia e reperfusão os pulmões podem ser alvo de lesão a distância como nos casos de choque, trauma ou ainda nos casos de transplante hepático. Objetivo: Avaliar o efeito protetor da N-acetilcisteína (NAC) sobre os pulmões após isquemia hepática. Métodos: Foram utilizados 12 ratos, machos, linhagem EPM-1 Wistar, separados aleatoriamente em dois grupos com seis animais (controle e experimento). Os animais de ambos os grupos foram submetidos à anestesia com cloridrato de quetamina e cloridrato de xilazina. Realizou-se a incisão mediana longitudinal, identificação do hilo hepático e da veia cava caudal. Quinze minutos antes do clampeamento injetou-se solução glicosada a 5% no grupo controle e NAC diluída em solução glicosada a 5% no grupo experimento. Os animais foram mantidos em isquemia hepática durante 30 minutos, sendo em seguida realizada toracotomia e remoção cirúrgica dos pulmões para avaliação histológica com coloração pela hematoxilina-eosina. Resultados: A análise dos cortes do parênquima pulmonar mostrou semelhança nos dois grupos estudados, ocorrendo colapso alveolar, infiltrado neutrofílico, congestão vascular e áreas hemorrágicas, compatíveis com a repercussão sistêmica da isquemia hepática. Conclusão: A NAC não modifica a lesão pulmonar decorrente da isquemia, à microscopia óptica.

Oxidative stress to human lymphocytes by xanthine oxidoreductase activity

The in vitro toxicity of the reactive oxygen species generating enzyme xanthine oxidoreductase (XOR) to human peripheral blood lymphocytes was studied after stimulation with phytohaemoagglutinin or anti-CD3/CD28 antibodies. Apoptosis and necrosis were induced by the XOR/hypoxanthine system in a time- and concentration-dependent manner. CD8+ lymphocytes showed a higher sensitivity than CD4+ cells to the XOR/hypoxanthine system. The occurrence of apoptosis was demonstrated by annexin-V binding to injured cell membrane, which was the most precocious alteration observed, followed by the increment of transglutaminase activity, which was significant at the lowest XOR concentration used. Nuclear damage was assessed by the increased hypodiploid nuclei and by DNA migration on gel electrophoresis, which turned to an apoptotic pattern before the occurrence of cell membrane necrotic lesions. Apoptosis was induced by XOR activity proportionally to substrate concentration and was prevented by the competitive enzyme inhibitor, allopurinol. The hydrogen peroxide scavenging enzyme, catalase, gave a higher protection than superoxide dismutase from the toxicity caused by the XOR/hypoxanthine system. Necrosis occurs in a variable percentage indicating that reactive oxygen species may trigger both apoptosis and necrosis in proliferating human lymphocytes, mostly depending on XOR concentration.

Pathophysiologic characteristics of hypovolemic shock

In the late 1800s, while caring for a trauma victim, Warren characterized shock as "a momentary pause in the act of death." A great deal about shock has been discovered since this first description. Dorland's Medical Dictionary defines shock as a condition of profound hemodynamic and metabolic disturbance characterized by failure of the circulatory system to maintain adequate perfusion of vital organs. Shock is now being defined at the cellular level as the inadequate delivery of nutrients to the cells of the body. Because oxygen is the only nutrient that cells cannot store in any appreciable quantity, shock is also equivalent to inadequate oxygen delivery (DO2). Although there are many types of shock, this article concentrates on the pathophysiologic characteristics of hypovolemic shock.

Hepatoenteric ischemia-reperfusion increases circulating heparinoid activity in rabbits

PURPOSE

The purpose of this study was to determine if an increase in circulating heparinoid activity contributes to the hemostatic abnormalities associated with hepatoenteric ischemia-reperfusion.

MATERIALS AND METHODS

Anesthetized rabbit (n = 18) underwent thoracic aorta occlusion for 30 minutes with a balloon catheter, followed by 30 minutes of reperfusion. Blood samples were obtained after 30 minutes of equilibration and 30 minutes of reperfusion. Hemostatic function was assessed by changes in the thrombelastographic variables R (reaction time), alpha (a measure of the speed of clot formation), and G (a measure of clot strength). Thrombelastography was performed on blood without platelet inhibition in the presence or absence of heparinase (n = 9 rabbits). Additional samples (n = 9) were exposed to cytochalasin D (platelet inhibitor) with or without heparinase.

RESULTS

Compared with preischemic values, blood samples with intact platelet function obtained during reperfusion demonstrated a decrease in hemostatic function evidenced by a significant (P<.05) increase in R, decrease in alpha, and decrease in G. R, alpha, and G values of samples without platelet inhibition exposed to heparinase did not significantly change after ischemia. Blood samples exposed to cytochalasin D displayed a similar pattern.

CONCLUSION

An increase in circulating heparinoid activity significantly contributes to the hemostatic disorder associated with hepatoenteric ischemia-reperfusion in rabbits.

Thoracic aorta occlusion-reperfusion decreases hemostasis as assessed by thromboelastography in rabbits

Perioperative hemorrhage and thrombosis are serious complications associated with major vascular surgery. We hypothesized that thoracic aortic occlusion-reperfusion in rabbits would adversely affect hemostasis as assessed by thromboelastographic variables (reaction time, alpha angle and G [a measure of clot strength]). Isoflurane-anesthetized rabbits underwent either sham operation (n = 10) or 30 min of aortic occlusion followed by 90 min of reperfusion (n = 10). Blood samples (350 microL) were exposed to 10 microL of either 0.9% NaCl or cytochalasin D (a platelet inhibitor, 10 microM final concentration) and analyzed for 1 h by using thromboelastography after 30 min of postpreparation equilibration and at 30 and 90 min of reperfusion. Aortic occlusion-reperfusion resulted in a significant (P: < 0.05) increase in reaction time, decrease in alpha angle, and decrease in G at 30 and 90 min of reperfusion compared with the sham-operated group. The decrease in hemostatic function after aortic occlusion-reperfusion was observed to the same degree in samples with or without platelet inhibition. There were no significant differences in platelet concentration between the sham-operated and aortic occlusion-reperfusion groups. Aortic occlusion-reperfusion decreased hemostatic function in rabbits primarily by decreasing the coagulation factor-dependent, platelet-independent contribution to clotting.

IMPLICATIONS

Thoracic aortic occlusion-reperfusion decreased hemostatic function in rabbits primarily by decreasing the coagulation factor-dependent, platelet-independent contribution to clotting. This decrease in hemostatic function may contribute to hemorrhagic complications associated with major vascular surgery.

Systemic and mesenteric hemodynamics, metabolism, and intestinal tonometry in a rat model of supraceliac aortic cross-clamping and declamping

OBJECTIVE

To describe systemic and mesenteric hemodynamics, metabolism, and intestinal tonometry in a rat model of supraceliac aortic cross-clamping and declamping.

DESIGN

Prospective, randomized, experimental study.

SETTING

University cardiovascular research laboratory.

PARTICIPANTS

Twelve male anesthetized and ventilated Sprague-Dawley rats.

INTERVENTION

Supraceliac aortic cross-clamping was performed for 30 minutes, followed by declamping and reperfusion for 180 minutes or sham clamping and sham declamping.

MEASUREMENTS AND MAIN RESULTS

Mean arterial blood pressure; abdominal aortic, superior mesenteric, and carotid artery blood flow; intestinal mucosal tonometry; hemoglobin; lactate; and blood gases were measured before and after 30 minutes of aortic cross-clamping and 15, 30, 60, 120, and 180 minutes after declamping during reperfusion. Aortic cross-clamping induced an increase in mean arterial pressure (117+/-20 mm Hg to 147+/-12 mm Hg), an increase in right atrial hemoglobin saturation(66%+/-11% to 81%+/-6%), an increase in lactate levels (1.7+/-0.7 mmol/L to 4.3+/-1.3 mmol/L), and an increase in tonometric PCO2 (49.6+/-5.0 mm Hg to 75.6+/-8.6 mm Hg). Three hours of reperfusion after declamping resulted in significantly decreased mean arterial pressure (38+/-10 mm Hg); decreased aortic (101+/-12 mL/min/kg to 57+/-32 mL/min/kg), mesenteric (19+/-4 to 13+/-6 mL/min/kg), and carotid (12+/-4 mL/min/kg to 5+/-3 mL/min/ kg) blood flows; and elevated lactate levels (4.2+/-2.0 mmol/L). Tonometric PCO2 had normalized to baseline levels (51.9+/-3.8 mm Hg), but PCO2 gap was significantly higher than in sham clamped rats (17.9+/-7.8 mm Hg v. 7.0+/-2.6 mm Hg).

CONCLUSIONS

Hemodynamic and metabolic effects of aortic cross-clamping and declamping known from large animal models are reproducible using a rat model. Intestinal tonometry indicated mesenteric ischemia during aortic cross-clamping, which was reversible to preclamp values within 30 minutes of reperfusion after declamping.

A CD18 monoclonal antibody reduces multiple organ injury in a model of ruptured abdominal aortic aneurysm

The role of CD18 antibody (anti-CD18) in remote and local injury in a model of ruptured abdominal aortic aneurysm repair was investigated. Rats were divided into sham, shock, clamp, and shock + clamp groups. Shock + clamp animals received anti-CD18 or a control monoclonal antibody. One hour of hemorrhagic shock was followed by 45 min of supramesenteric aortic clamping. Intestinal and pulmonary permeability to (125)I-labeled albumin was determined. Myeloperoxidase (MPO) activity, F(2)-isoprostane levels, and transaminases were also measured. Only shock + clamp resulted in statistically significant increases in pulmonary and intestinal permeability, which were associated with significant increases in MPO activity and F(2)-isoprostane levels. Treatment with anti-CD18 significantly decreased intestinal and pulmonary permeability in shock + clamp animals. These reductions were associated with significantly reduced intestinal and hepatic MPO activity and pulmonary F(2)-isoprostane levels and reduced alanine and aspartate aminotransferase levels; however, anti-CD18 had no effect on intestinal or hepatic F(2)-isoprostane levels or on pulmonary MPO activity. These results suggest CD18-dependent and -independent mechanisms of local and remote organ injury in this model of ruptured abdominal aortic aneurysm.

Lesão pulmonar de reperfusão

A lesão de isquemia-reperfusão constitui-se em um evento fisiopatológico comum a diversas doenças da prática clínica diária. O pulmão pode ser alvo da lesão de isquemia-reperfusão diretamente, como no edema pulmonar após transplante ou na resolução de tromboembolismo; ou ainda ser atingido à distância, como nos casos de choque ou por lesão de reperfusão em intestino ou em membros inferiores, como ocorre no pinçamento da aorta, utilizado nas cirurgias de aneurisma. Dentre os mediadores envolvidos na lesão de isquemia-reperfusão, foram identificados espécies reativas tóxicas de oxigênio (ERTO), mediadores lipídicos, como a tromboxana, moléculas de adesão em neutrófilos e endotélio, fator de necrose tumoral, dentre outros. As medidas terapêuticas para a lesão de reperfusão ainda são utilizadas no plano experimental e em poucos estudos clínicos. São utilizados: antioxidantes, bloqueadores de mediadores lipídicos, inibidores da interação entre leucócito e endotélio ou substâncias que favoreçam o fluxo sanguíneo pós-isquêmico.

Hypercapnic acidosis may attenuate acute lung injury by inhibition of endogenous xanthine oxidase

Relative hypoventilation, involving passively-or "permissively"-generated hypercapnic acidosis (HCA), may improve outcome by reducing ventilator-induced lung injury. However, the effects of HCA per se on pulmonary microvascular permeability (Kf,c) in noninjured or injured lungs are unknown. We investigated the effects of HCA in the isolated buffer-perfused rabbit lung, under conditions of: (1) no injury; (2) injury induced by warm ischemia-reperfusion; and (3) injury induced by addition of purine and xanthine oxidase. HCA (fraction of inspired carbon dioxide [FICO2] 12%, 25% versus 5%) had no adverse microvascular effects in uninjured lungs, and prevented (FICO2 25% versus 5%) the increase in Kf,c following warm ischemia-reperfusion. HCA (FICO2 25% versus 5%) reduced the elevation in Kf,c, capillary (Pcap), and pulmonary artery (Ppa) pressures in lung injury induced by exogenous purine/xanthine oxidase; inhibition of endogenous NO synthase in the presence of 25% FICO2 had no effect on Kf,c, but attenuated the reduction of Pcap and Ppa. HCA inhibited the in vitro generation of uric acid from addition of xanthine oxidase to purine. We conclude that in the current models, HCA is not harmful in uninjured lungs, and attenuates injury in free-radical-mediated lung injury, possibly via inhibition of endogenous xanthine oxidase.

Upregulation of xanthine oxidase by lipopolysaccharide, interleukin-1, and hypoxia. Role in acute lung injury

LPS and selected cytokines upregulate xanthine dehydrogenase/xanthine oxidase (XDH/XO) in cellular systems. However, the effect of these factors on in vivo XDH/XO expression, and their contribution to lung injury, are poorly understood. Rats were exposed to normoxia or hypoxia for 24 h after treatment with LPS (1 mg/kg) and IL-1beta (100 microg/kg) or sterile saline. Lungs were then harvested for measurement of XDH/XO enzymatic activity and gene expression, and pulmonary edema was assessed by measurement of the wet/dry lung weight ratio (W/D). Although treatment with LPS + IL-1beta or hypoxia independently produced a 2-fold elevation (p < 0. 05 versus exposure to normoxia and treatment with saline) in lung XDH/XO activity and mRNA, the combination of LPS + IL-1beta and hypoxia caused a 4- and 3.5-fold increase in these values, respectively. XDH/XO protein expression was increased 2-fold by hypoxia alone and 1.3-fold by treatment with LPS + IL-1beta alone or combination treatment. Compared with normoxic lungs, W/D was significantly increased by exposure to hypoxia, LPS + IL-1beta, or combination treatment. This increase was prevented by treatment of the animals with tungsten, which abrogated lung XDH/XO activity. In conclusion, LPS, IL-1beta, and hypoxia significantly upregulate lung XDH/XO expression in vivo. The present data support a role for this enzyme in the pathogenesis of acute lung injury.

Hypoxia-reoxygenation is as damaging as ischemia-reperfusion in the rat liver

OBJECTIVE

We hypothesized that the extent of injury and release of xanthine oxidase, an oxidant generator, into the circulation would be less in normal-flow hypoxia-reoxygenation than in equal duration no-flow ischemia-reperfusion.

DESIGN

Randomized study.

SETTING

University-based animal research facility.

SUBJECTS

Male Sprague-Dawley rats.

INTERVENTIONS

The livers were isolated, perfused, and then randomly subjected to 2 hrs of hypoxia (normal flow, low oxygen) or ischemia (no flow, no oxygen), and 2 hrs of reperfusion. Hepatocytes were also isolated, and were subjected to either: a) hypoxia (0, 2, 4, and 6 hrs); or b) hypoxia (2 and 4 hrs) with reoxygenation (2 hrs).

MEASUREMENTS AND MAIN RESULTS

The extent of liver injury (as assessed by release of hepatocellular enzymes) and the release of xanthine oxidase were measured from isolated-perfused rat livers and cultured hepatocytes. The pattern of release of xanthine oxidase in isolated-perfused liver effluent was different in hypoxia-reoxygenation compared with ischemia-reperfusion. During hypoxia, xanthine oxidase gradually increased in the effluent; then, the xanthine oxidase decreased to low concentrations during reoxygenation. After ischemia, there was a sharp spike in xanthine oxidase at 1 min of reperfusion, with a rapid decrease to low concentrations. The total release of xanthine oxidase during hypoxia-reoxygenation was similar to that during ischemia-reperfusion. Lactate dehydrogenase and other markers of liver injury showed a pattern of release that was similar to that of xanthine oxidase, but the total release of markers was not different between the two groups. In hepatocytes, most of the release of enzymes occurred in hypoxia, and the rate of release was not different between hypoxia and hypoxia-reoxygenation.

CONCLUSIONS

Hypoxia-reoxygenation results in as much damage to the liver as ischemia-reperfusion, and results in the release of a similar amount of oxidant-producing xanthine oxidase into the circulation.

PentaLyte decreases lung injury after aortic occlusion-reperfusion

Lung injury often occurs after hepatoenteric ischemia, with xanthine oxidase (XO, an oxidant-generating enzyme), released from reperfusing liver and intestines, mediating a significant component of this injury. Since pentastarch administration decreases intestinal reperfusion injury, we determined whether resuscitation with PentaLyte (a pentastarch-containing solution) would decrease hepatoenteric reperfusion injury, xanthine oxidase release, and concomitant lung injury after aortic occlusion- reperfusion. Aortic occlusion was established in rabbits for 40 min, and was followed by 3 h of reperfusion, during which either PentaLyte or lactated Ringer's solution-based resuscitation was administered. Sham-operated animals served as controls. Hepatoenteric reperfusion injury, as manifested by release of the enzyme aspartate aminotransferase and decreased gastric intramucosal pH, was significantly (p < 0.0167) attenuated by PentaLyte administration after aortic occlusion-reperfusion, as compared with its occurrence in animals given lactated Ringer's solution. The release of XO after aortic occlusion-reperfusion was 4-fold smaller after PentaLyte administration than after resuscitation with lactated Ringer's solution (p < 0.05). Pulmonary injury, as defined by an increase in bronchoalveolar lavage fluid (BALF) protein content and lactate dehydrogenase (LDH) activity, was 4-fold less after PentaLyte administration following aortic occlusion-reperfusion than after administration of lactated Ringer's solution (p < 0.05). We conclude that remote pulmonary injury is significantly decreased by concomitant PentaLyte-mediated reduction of hepatoenteric reperfusion injury and XO release.

Cholestatic liver injury increases circulating TNF-alpha and IL-6 and mortality after Escherichia coli endotoxemia

We employed a bile duct ligation (BDL) model of cholestatic liver injury to test the hypothesis that this form of preexisting hepatic dysfunction alters the kinetics of circulating TNF-alpha and IL-6 after Escherichia coli endotoxemia, thereby augmenting mortality and lung injury by a TNF-alpha:leukotriene (LT) axis of inflammation. Male rats were catheterized 13 d after BDL or sham surgery and studied while awake 18 to 24 h later. Cholestasis after BDL was confirmed by baseline serum bilirubin (BDL = 7.34 +/- 0.72 mg/dl, mean +/- SEM, n = 17 versus Sham = 0.25 +/- 0.07, n = 20; p < 0.005) and histopathology. Sham and BDL animals received E. coli lipopolysaccharide serotype O55:B5 (LPS, 5 mg/kg i.v.) or 0.9% NaCl (NS) ending at t = 0 and were monitored over 24 h for vital signs and hemodynamics. In parallel studies, lipoxygenase inhibition was performed using diethylcarbamazine or the 5-lipoxygenase activating-protein inhibitor MK-886. Blood was collected at baseline and at t = 1.5, 3.5, and 24 h for formed elements and for serum endotoxin, TNF-alpha, IL-6, bilirubin, and alanine aminotransferase (ALT). Organs were evaluated at 24 h for histopathology, including neutrophil (PMN) densities and wet/dry weight (W/D) ratios. Cholestasis reduced survival after otherwise nonlethal endotoxemia, with seven of 11 BDL + LPS rats dying within 24 h versus no deaths in BDL + NS (n = 6), Sham + LPS (n = 14), or Sham + NS (n = 6) animals (p < 0.01). Despite equivalent serum endotoxin between groups, circulating TNF-alpha was 8-fold higher in BDL + LPS than in Sham + LPS rats at 1.5 and 3.5 h (p < 0.001), whereas serum TNF-alpha did not differ between BDL + NS and Sham + NS rats. IL-6 likewise was increased differentially by 1.5 h in BDL + LPS animals (11.98 +/- 2.42 ng/ml) versus Sham + LPS rats (3.05 +/- 0.58 ng/ml, p < 0.05). Hypothermia, bradycardic hypotension, and leukopenia were most severe and prolonged in BDL + LPS rats, which also had significantly higher ALT values, W/D ratios, and organ PMN counts. LT inhibition failed to reduce BDL-related differences in serum cytokines or survival after endotoxemia. Thus, cholestasis augments inflammatory responses to gram-negative endotoxemia, sensitizing the host to enhanced fluid flux in multiple organs and to mortality by a LT-independent mechanism.

Hextend (hetastarch solution) decreases multiple organ injury and xanthine oxidase release after hepatoenteric ischemia-reperfusion in rabbits

OBJECTIVE

We hypothesized that multiple organ injury and concentrations of xanthine oxidase (an oxidant-generating enzyme released after hepatoenteric ischemia) would be decreased by the administration of a bolus of a colloid solution at reperfusion.

DESIGN

Randomized, masked, controlled animal study.

SETTING

University-based animal research facility.

SUBJECTS

Fifty-four New Zealand white male rabbits, weighing 2 to 3 kg.

INTERVENTIONS

Anesthetized rabbits were assigned to either the hepatoenteric ischemia-reperfusion group (n = 27) or the sham-operated group (n = 27). Hepatoenteric ischemia was maintained for 40 mins with a balloon catheter in the thoracic aorta, followed by 3 hrs of reperfusion. Each group was randomly administered a bolus of one of three fluids at the beginning of reperfusion: Hextend (hetastarch solution); 5% human albumin; or lactated Ringer's solution. The investigators were masked as to the identity of the fluid administered.

MEASUREMENTS AND MAIN RESULTS

Multiple organ injury was assessed by the release of lactate dehydrogenase activity into the plasma and by indices of gastric and pulmonary injury. Circulating lactate dehydrogenase activity was significantly greater (p < .001) in animals receiving lactated Ringer's solution than in rabbits receiving either colloid solution. Gastric injury (tissue edema, Histologic injury Score) was significantly decreased (p < .01) by administration of both colloid solutions. Lung injury (bronchoalveolar lavage lactate dehydrogenase activity) was significantly decreased (p < .05) by the hetastarch solution administration. The hetastarch solution administration resulted in 50% less xanthine oxidase activity release during reperfusion compared with albumin or lactated Ringer's solution administration (p < .001).

CONCLUSION

We conclude that multiple organ injury and xanthine oxidase release after hepatoenteric ischemia-reperfusion are decreased by colloid administration.

Xanthine oxidase mediates myocardial injury after hepatoenteric ischemia-reperfusion

OBJECTIVES

To determine if myocardial injury results from hepatoenteric ischemia-reperfusion. We also proposed to determine if this remote heart injury is mediated by a xanthine oxidase-dependent mechanism.

DESIGN

Randomized, controlled animal study.

SETTING

University-based animal research facility.

SUBJECTS

Thirty-six New Zealand white male rabbits, weighing 1.8 to 3 kg.

INTERVENTIONS

Anesthetized rabbits were randomly assigned to one of four groups (n = 9 per group): a) a sham-operated group; b) a sham-operated group pretreated with sodium tungstate (xanthine oxidase inactivator); c) an aorta occlusion group; and d) an aorta occlusion group pretreated with sodium tungstate. Descending thoracic aorta occlusion was maintained for 40 mins with a 4-Fr Fogarty embolectomy catheter, followed by 2 hrs of reperfusion.

MEASUREMENTS AND MAIN RESULTS

Myocardial injury, manifested by increased circulating creatine kinase-MB fraction activity, was significantly associated with aortic occlusion and reperfusion (p < .05). Sodium tungstate pretreatment significantly (p < .05) reduced circulating and myocardial xanthine oxidase activity. Xanthine oxidase inactivation by sodium tungstate significantly decreased circulating creatine kinase-MB fraction activity after hepatoenteric ischemia-reperfusion (p < .05). Finally, circulating creatine kinase-MB fraction activity was significantly associated with circulating xanthine oxidase activity (r2 = .85; p < .001).

CONCLUSIONS

We conclude that remote myocardial injury is caused by hepatoenteric ischemia-reperfusion. The pathoetiology of this myocardial injury involves a xanthine oxidase-dependent mechanism.